1. Field of the Invention
The present general inventive concept relates to a dielectric layer, an MIM (Metal-Insulator-Metal) capacitor using the dielectric layer, and a method of forming the dielectric layer and capacitor using the dielectric layer.
2. Description of the Related Art
MIM (Metal-Insulator-Metal) capacitors are currently used in semiconductor technology as storage devices to store data due in part to their electrical characteristics. The electrical characteristics of MIM (Metal-Insulator-Metal) capacitors depend on the electrical characteristics of dielectric layer(s) formed therein as part of the capacitor device. Moreover, the electrical characteristics of the dielectric layer are largely divided into the leakage current characteristics and the dielectric characteristics. Experimentally, the leakage current characteristics of the dielectric layer closely depend on the impurities content, the composition ratio and the interface characteristics of the dielectric layer. The dielectric characteristics of the dielectric layer depend on the equivalent thickness of oxide within the dielectric layer.
More specifically, the dielectric layer of an MIM capacitor is deposited by supplying both a metal source material and an oxidation agent in order to form a dielectric layer having a high dielectric constant and excellent leakage current characteristics, through either an Atomic Layer Deposition (ALD) process or a Chemical Vapor Deposition (CVD) process. Further, an oxidizing agent plays very important role to remove residual un-reacted by product such as hydrogen carbon bonding. The residual hydrogen carbon bonding in formed oxide layer is then effectively removed through a chemical reaction with sufficient oxidizing agent. Further, amount of the residual hydrogen carbon impurities are as function of the concentration and supplying amount of the oxidizing agent.
FIG. 1 is a chart illustrating leakage currents of an MIM capacitor based on a supplying time of an oxidizing agent when forming a dielectric layer of the MIM capacitor. In FIG. 1, the MIM capacitor represented in the illustrated chart includes a ZrO2 layer formed by an ALD process. More specifically, the solid line (a) represents leakage current of the MIM capacitor when an oxidizing agent is supplied for a time of about 10 seconds; the dotted line (b) represents leakage current of the MIM capacitor when an oxidizing agent is supplied for a time of about 5 seconds; and the solid line (c) represents leakage current of the MIM capacitor when an oxidizing agent is supplied for a time of about 3 seconds. It is evident by the results illustrated in FIG. 1 that leakage current characteristics are improved proportionally with an increase in the supplying time of the oxidizing agent.
FIG. 2 is a chart illustrating breakdown voltages vs. the effective equivalent oxide thickness [EOT] of an MIM capacitor in accordance with a supplying time of an oxidizing agent. As can be seen from the chart of FIG. 2, as the supplying time of an oxidizing agent is increased, the breakdown voltage increases while the EOT also increases. More specifically, as can be seen by the line (a) represented by squares, when the oxidizing agent supplying time is approximately 10 seconds, a high breakdown voltage of an MIM capacitor results while the leakage current characteristics thereof is low. As the supplying time of the oxidizing agent is decreased to approximately 5 seconds, as illustrated in line (b), the breakdown voltage of an MIM capacitor is lowered while the leakage current characteristics thereof increases, resulting in less desirable properties of the MIM capacitor. Finally, line (c) illustrates where the supplying time of the oxidizing agent in decreased further to approximately 3 seconds, resulting in a further decrease in the breakdown voltage of an MIM capacitor and even higher leakage current characteristics. Therefore, as the supplying time of the oxidizing agent is increased, the leakage current characteristics of the capacitor are most desirable.
FIG. 3 illustrates a graph of the intensity of carbon contents (cnts/s) vs. time (sec) in a dielectric layer as different amounts of oxidizing agent are supplied during formation of the dielectric layer. As illustrated in FIG. 3, as the supplying time of the oxidizing agent is increased, the intensity of the carbon content in the dielectric layer decreases and the amount of dielectric components increases. Thus, it has been determined that the concentration and supplying amount of the oxidizing agent (or oxidation source) have to be increased in order to improve the leakage current characteristics of the dielectric layer.
However, when the supplying time of the oxidizing agent is increased in cycles, problems exist.
Above all, an increase in the supplying time of the oxidizing agent results in a serious increase in the time required in manufacturing the capacitor results. Furthermore, growing of interfacial layer between dielectric layer and bottom electrode increases the effective equivalent oxide thickness (EOT) when the supplying time of the oxidizing agent is increased. FIG. 4 illustrates how the concentration of interfacial oxide such as TiO2 (in special case as TiN electrode) increases with time as the amount of oxidizing agent increases.